Work function (redirected from work functions)

The amount of photon energy required to cause an electron to be emitted from a material.

---

Work function (electronics)

A quantity with the dimensions of energy which determines the thermionic emission of a solid at a given temperature. For metals, the work function may also be determined by measuring the photoemission as a function of the frequency of the incident electromagnetic radiation: the work function is then equal to the minimum (threshold) frequency for which electon emission is observed times Planck's constant h (= 6.63 × 10^-34 joule second). The work function of a solid is usually expressed in electronvolts.

The work function of metals varies from one crystal plane to another and also varies slightly with temperature. For a metal, the work function has a simple interpretation. At absolute zero, the energy of the most energetic electrons in a metal is referred to as the Fermi energy; the work function of a metal is then equal to the energy required to raise an electron with the Fermi energy to the energy level corresponding to an electron at rest in vacuum. The work function of a semiconductor or an insulator has the same interpretation, but in these materials the Fermi level is in general not occupied by electrons and thus has a more abstract meaning. See Field emission, Photoemission, Thermionic emission

---

Work function (thermodynamics)

The thermodynamic function better known as the Helmholtz energy, A = U - TS, where U is the internal energy, T is the thermodynamic (absolute) temperature, and S is the entropy of the system. At constant temperature, the change in work function is equal to the maximum work that can be done by a system (ΔA = w_max). See Free energy